Circuit breaker



Sept. 24, 1935.

H. D. DORFMAN CIRCUIT BREAK'ER Filed July 12, 1933 INVENTR #ZZ/3f!) Q/fmm.

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ATTORNE bolt 3i to the terminal 34 of the U-shaped bimetallic trip element 33, and iinally through that element, the other terminal 36, and the terminal conducting strip 35 to the other terminal con-tact 5.

The structural details of the circuit breaker operating mechanism 9 and the arc extinguisher I3 are not important parts of this invention, and

any suitable mechanism which is adapted to engage a trip latch may be used. I prefer, however, to utilize a mechanism similar to that disclosed in my copending application, Serial No. 600,660, filed on March 23, 1932 and assigned to the same assignee as this invention.

The switch member Il has a channel shaped frame 31 which is pivoted to the U-shaped frame 3! of the circuit breaker operatingvmechanisrn 9 through the agency of a pivot pin El. The resilient switch arm 23 is preerablyconstructed ot spring steel, and, as previously pointed out, the moving contact 2| is rigidly aiiixed to the 4free end thereof by means of a rivet 43. The switch arm itself is affixed to the channel shaped frame by means of two other rivets I5. The conducting shunts 25 are electrically connected to the moving contact 2l at one end, and are provided with terminals at the other end adapted to be engaged by the screw 21. Round spacing washers il are provided to position the switch member frame 3l between the up-standing sides of the frame ll of the operating mechanism.

I prefer to use arc resisting material for both the moving and the stationary contacts, the former being composed of finely divided silver and graphite compressed into a. conglomerate mass. and the latter being composed of a silver molyb denum alloy.

The arc extinguisher I3 is preferably ci the spaced-plate type in which :a plurality of slotted plates of magnetic material, each insulated from the adjacent plates and having a slot therein. are provided. The slots in the plates are of substantially the same outline as the moving contact and the extinguisher is positioned closely adjacent the arc path. The magnetic plates so alter the field adjacent the arc that it is moved into the spaces between the plates 'where it is quickly cooled and extinguished.

In the structure shown in l, the magnetic plates 4H having slots therein are assembled be tween tivo end plates 5l of insulating materif;` projecting lugs lnot shown) being provided .in the magnetic plates 19 lor engaging the end plates E l.

The operating mechanism 9 comprises, ingeneral, a U -shapcd base 39, pair olf `toggle links 53 and 55 for engaging and actuathig the frame 31 oi' the switch member Il, a releasable carrier or trigger 51 for restraining the toggle links in an operative position, an operating member I1, and a pair of over-center springs 59 for connecting the operating member I1 to the knee of the toggle links. The U-shaped base 39 as previously pointed out, is fastened to the insulating base of the circuit breaker proper by means oi two screws 5| that engage suitable threaded openings in the base. The pivot pin Il which provides a pivot point for the switch member l i extends'through alined openings in the opposing sides of the U. Other openings are provided for the reception of the pivot pins 63f-one on either side of the U which provide pivot points for the bifurcatedl portion G5 of the operating member l1.

The lower end (with respect to the basel) of the toggle link 53 is pivoted to the frame 31-of the switch member il by means of a pivot pin B1. The upper end of the toggle link 53 is pivoted to -the U-shaped base.

one end of the second toggle link 55 by means of the knee pivot pin 69. One of the operating springs 55 engages each end of the knee pivot pin 65| and thus serves to operatively connect the knee of the toggle with, the operating member l1. The carrier 51, which is pivoted about the pin 1I provides a releasable restraining means for holding the toggle links in an operative positionthe upper end of the toggle link 55 beingpivotally fastened to the carrier 51 through the agency of a. pin 13. K The movement of the carrier about its pivot pin in a clockwise direction is limited by the projection 15 which extends inwardly from one side of the U-shaped base 39. The limits of motion of the biiurcated portion B5 of the operating member are delinedby the off-set projections 11 and 15 forming a part oi the sides of The carrier 51 is provided with a projecting portion 8l adapted to engage the trip device 1A The trip device l includes a current carrying bimetallic member 33, a latch 83 for engaging the operating mechanism 5, and a member 85 intel'A mediate the latch and the electro-responsive elel. and 2, p

ment. .As shown particularly in Figs. the latch is supported on a pivot pin 'nich extends through opposed holes in the upstacd ing sides oi a pair oi' bracket members 89, be bracket members being aiiixed to the by tofu screw bolts lll.

The latch lili is shown particularly in liti and includes a rectangular slot 93 [or `the end Bi of the carrier lever 51, a rearwardly err-- tending portion liti for engaging the intermediate member 85, and an lip-standing projection lll,

the. function of which'vvill be described in some detail later. The latch lili is biased to "h unlatched position by means oit the spring The intermediate member B5 pivo y cupported adjacent the point oi support oi' the l1i metallic element by means two sinH arms lili, anxed to 'the base by the screw 9i, and the tivo pivot pins im. Ecco. oi tb.. support lill has inwardly extending pi'o jection Miti h serves as a stop for li `itinlg; the motion i the intermediate member o clockwise di' :ion about its pivot point.

A pair of plate members llll and i019 secured to the body portion oi the ini member Bil by means oi a rivet lll. member lill' is utilized as an anchor .m the Hit which connects intermediate member The is utilized a stop for the latch. nttrrm mediate member B5 has an overhanging portion Figs. l. 2, and 3, includes a pair of plates l2! of insulating material held together by a pair of metallic plates |23 and a pair of rivets |25 which extend through enlarged openings in the end l l S of the bimetallic member.

The carrier member 51 is at all times biased in a clockwise direction by the reaction force 0i' the over-center springs 59. This force must be balanced by the latch as, and in order to secre accurate operation of the trip device it is necessary that the location of the pivot points and the point of application of the balancing force be such that practically none'of the reaction force must b e overcome bythe bimetallic element when moving the intermediate member to tripped position.

This desired result is accomplished in the above described embodiment of my invention by causing the entire static balancing force to be supplied by theinwardly projecting stops |05 which limit the clockwise movement of the intermediate member 85, and by so proportioning the intermediate member that it can' be moved to the tripped position without moving the latch 88 against the biasing force transmitted through the carrier 51;- the `vtotal force which must be supplied by the bimetallic element when moving to the tripped position being merely that necessary to overcome the biasing action of the spring H3 and the sliding friction opposing the disengaging of the end of the latch'83 by the latch plate |09 afilxed to the intermediate member 85.

The circuit breaker is shown in the closed position in Fig. 1, and it will be noted that the toggle has been moved to the over-center latched position. To open the contacts manually the operating handle I1 is moved in a counter-clockwise direction about its pivot point, the pins 88; shortly before the operating handle |1 has reached its limit of travel in the counter clockwise ldirection the line of action of the overcenter springs 59 is brought to the left of the center line of the toggle. This results in the producing of a component of force which moves the toggle to the collapsed position. Since movement of the knee of the toggle from the position shown in Fig. l toward the collapsed position results in a progressive increasing of the force causing the movement,- the opening operation,once started, takes place automatically and results in the separation of the contacts with a snapaction. 1

The closing operation is substantially the reverse of the opening operation. 'I'he handle is moved in a clockwise direction, the resulting tension of the over-center springs causes the knee of the toggle to move toward the closed circuit position, and since the same progressive increase lin .the component acting upon the'knee of the toggle is present,`th'e closing operation is likewise carried on with a snap action.

Upon the occurrence of a predetermined overload condition the increased 12R loss in the current carrying bimetallic element 33 results in. the production of sumcieni; heating to cause that element to deflect away from the operating mechanism '9. If the overload persists for a suiilcient interval of time, this deection becomes, great enough to move the intermediate member 85 from the position shown in'Fig. 1 to the position shown in Fig. 3, the plate |09 being moved out of en gagement with the end 95 of the latch 83. This releases the latch 83 and allows the carrier 51 to move freely in a clockwise direction about its pivot pin 1| under the influence of the reaction' forces of the over-center springs 59. Almost immediately, the end of the togglel link 55 which is pivoted on the carrier 51 is moved a sufficient distance to the right of the center line of the` toggle to cause the toggle tocollapse as a result of the tension forcelapplied to the knee pivot pin 69 by the over-center springs 59. The switch member frame'h rotates about its pivot pin 4| and moves the contact 2| to the open circuit position in exactly the same manner as described for manual operation. Due to the change in the position of the knee pivot pin 69, the operating handle is biased in a counter-clockwisedirection but moves only to the middle position due to the engagement of the downwardly projecting member |21 with the end |29 of cradle 51. This movement of the handle to the mid-position following the tripping of the breaker serves as a ready indicating means for showing that the circuit has been opened in response to an abnormal electrical. condition.

During the tripping operation, the intermediate 15 member 85 is moved against the biasing action of the spring H3 connecting that member and the latch 88. immediately following the disengaging of the end 95 of the latch 83 by the plate |09 aillxed to the intermediate member 85, the 20 latch becomes free to rotate under ,the combined forces of its own biasing spring 99 and the reaction force transmitted through the cradle 51. The mechanism immediately moves to the position shown in Fig. 3 and it becomes readily apparent 25 that all external forces biasing the intermediate member 85 against movement by the bimetallic element 88 are at once released due to the move- Y ment of the projecting portion 91 of the latch 88. Thus, following the tripping of the breaker, -30 thebimetallic element4 83 is free to move without having to overcome lany external force tending to prevent such movement. This is particularly desirable when interrupting Qverloads of large magnitudes, because, due to the' steepness of 3 the wave front and the resulting rapidity with Jhich such overloads reach 'a dangerously large l The movement of the bimetallic member, therefore, does not occur simultaneously with the occurrence of the overload, nor does it occur simul-` taneously with its own heating due to the mechanical inability of the metal to expand in- 4,-, stantaneously. Further, the heating continues after the trip device has been actuated due to the time required to extinguish the arc, and if any external force acts upon the bimetallic element during-the time of arc extinction, that element, 50 due to the lowering of its elastic limit as a result of the high temperature to which the element is heated, may take on a permanent set. If this happens, the calibration of the device is entirely destroyed and serious damage may result to the 55 equipment which is protected thereby upon the occurrence of successive overload conditions. The trip devices heretofore known'in the art have not been provided with means for removing -all external stressfrom the bimetallic elements im- 60 mediately upon the actuation of the trip device, and it is to this feature that my invention is particularly directed. Y

The entire mechanism is entirely resettable by movement of the operating handle' l1. As menc5 tioned above, the'projection |21 which extends downwardly from the operating handle l1 engages the end |29 of cradle 51 when the breaker. A is inv the tripped position. To reset the mechanism and the trip device, the handle is moved to 70 the full o position. This movement causes a rotation of the cradle 51 in a counter-clockwise direction about its pivot pin 1|, the end 8| of cradle 51 engages the bottom of the rectangular slot 93 in the latch 83, the latch is rotated in 75 a clockwise direction about its pivot pin 81, the spring H3 connecting the latch 83 and the intermediate member is tensioned, thereby moving the intermediate member 85 to the position shown in Fig. 1, whereupon the projecting end of the latch reengages the latch plate'l09. 'I'he breaker may then be closed manually as described in the previous paragraph.

The operating mechanism 9 is trip free of the operating handle l1 because the movement of cradle 51 following its release by the trip latch is independent of the position of the handle, and because the parts are so proportioned that the toggle cannot be held from collapsing following the release of the cradle.

It will thus be seen that I have disclosed an improved circuit breaker trip device utilizing a bimetallic electro-responsive element which is normally free from external stress, and which is stressed only during that portion oi its movement which is necessary to cause the release of the latch holding the trip device in the untripped position, In addition, I have disclosed how this principle may be utilized in combination with a trip device having means inherent therein for equaliz- While in accordance with the patent statutes,

I have given the foregoing details of a practical embodiment of my invention, it is to be understood that many of these details are merely illustrative and the variation in their precise form will be desirable in some applications. I desire, therefore, that the language of the accompanying claims shall be accorded the broadest reasonable construction and that my invention be limited only by what is explicitly stated in the claims and by the prior art.

I claim as my invention:

1. In a trip device for a circuit interrupter a thermally responsive element of bimetallic material, and a tripping mechanism adapted to be actuated thereby, said tripping mechanism including a mgber movable` in response to movement of 'said element to cause said mechanism to move to the tripped position, means biasing said member against movement, and means for rendering said biasingy means ineffective when said member has been moved to the tripped'position.

2. In a trip device for a circuit interrupter, an electro-responsive element, a latch, a latch retaining means adapted to be moved by said element to release said latch, means biasing said retaining means to the latch-retaining position, and means for rendering saidbiasing means ineffective lmmediately following the release` of said latch by said retaining means.

3. In a trip device for a circuit interrupter, a thermally responsive element of bimetallic material, a `tripping means adapted to be actuated thereby, means biasing said tripping means to the untripped position, and means for reducing the force exerted by 'said biasing means as soon as said tripping means has been'moved to the tripped position by said thermally responsive element.

4. In a trip device for a circuit interrupter, a

V thermally responsive element of bimetallic material supported adjacent one end and having a freely movable portion at the other end, a latch, a pivotally suppprgtedlatch retaining means adapted to`l5e/m'oved by samedi, to release said latch, means biasing said retaining means againstmovement by said element, and means for relieving said element from the force exerted `aoiaeaa by said biasing means immediately following the release of said latch by said retaining means.

5. In a trip device for a circuit interrupter, a thermally responsive element of bimetallic material, supported at one end and having a freely movable portion at the other end, a latch, a latch actuating means pivowsupported adjacent the supported end of said bimetallic element and having a portion extending along the freely movable portion of said bimetallic element, said latch actuating means being adapted to be moved by said bimetallic element to release said latch, spring means biasing said actuating means to the untripped position, and means for rendering said biasing means ineffective immediately iol.- lowing the movement of said actuating means to the tripped position.

6. In a circuit interrupter, a switch member, for opening and closing the circuit, means for biasing said switch` member to one position, a

latch for releasably restraining said switch member against said biasing means, an electro-responsive device for releasing saidylatch, a member, intermediate said electro-"responsive device and said latchnpon which the force of said switch member biasing means acts, said intermediate member being engaged by said electro-responsive device to release said latch, means biasing said intermediate member to the latch engaged position, and means for causing said biasing means for said intermediate member to become'ineflective when said intermediate member has been moved a predetermined distance by said electro-responsive device.

'7. In a circuit interrupter, a switch member for opening and closing the circuit, means for biasing said switch member to the open position, a pivoted latch for releasably restraining said switch member in the closed'positionagainst the force of said i biasing means, an electro-responsive device in- Y cluding a bimetallic member for releasing said latch,l a pivotally mounted member, intermediate said electro-responsive devle'and said latch upon which the force of said switch member biasing means acts, said bimetallic member being adapted to engage said intermediate member to release said latch, spring means biasing said intermediate member against movement by said bimetallic member, and means for rendering said spring .biasing means for said intermediate member inmeans for causing said latch biasing means to 6 become ineffective when said latch means has been moved to release said switch member.

9. In electrical apparatus, a movable electroresponsive element, a latch means adapted to be actuated by said electro-responsive element, a spring for biasing said latch means against movement to the unlatched position by said electroresponsive element, andv support means for said spring, said support means causing said' spring to move toward'said electro-responsive element Cil and thereby unstress said spring when said latch n is released.

l0. In a trip device for a circuit interrupter, an electro-responsive element of bimetallic material, a latch means actuated thereby, and a spring intermediate said electro-responsive element and said latch means, said spring being aiiixed to support means forming a part of said latch means 'and being adapted to be` tensioned when said electro-responsive element moves to the tripped position to actuate said latch, said support means moving toward said electro-responsive element to reduce the stress of said spring as soon as said latch is caused to move to the tripped position by said electro-responsive element.

11. In a trip device for use with electrical apparatus, an electro-responsive element, a latch, a latch retaining means intermediate said latch and said electro-responsive element, 'said latch retaining means being adapted to be moved by said electro-responsive element to cause the release of said latch, means biasing said retaining means against movement by said electro-responsive element, and means operable to cause said electro-responsive element to be relieved of the force exerted by said biasing means opposing movement of said retaining means by said element immediately following a release of said latch by said retaining means.

12. In a trip device for use with electrical apparatus, a thermally responsive element of bimetallic material having a freely movable portion, a latch, a pivotally supported latch retaining means adapted. to be moved by said bimetallic element to effect the release of said latch, means biasing said retaining means against movement by-said element, and means for relieving said element from. the force exerted by said biasing means opposing movement of said latch retaining means by said element immediately following the release of said latch by said retaining means.

13. In a trip device for a circuit interrupter, a thermally responsive element of bimetallic material supported adjacent one end and having a f freely movable portion at the other end, a latch, a pivotally supported latch retaining member intermediate said latch and said thermally responsive element which is. adapted to be moved by said element to eifect the release ofA said latch, a resilient means biasing said retaining .member against movement by said thermally responsive element, and means for relieving said element from the force exerted by said biasing means opposing movement of said latch retaining means by said element immediately following the release or said latch by said retaining means.

14. In a trip device for a circuit interrupter, a thermally responsive element of bimetallic material having a freely movable portion, means 5 movable in response to movement of said element to cause actuation of said trip device, a spring biasing said actuating means against movement by said element, means normally preventing said spring means from causing said movable vmeans l0 to engage said electro-responsive element except during the tripping operation. and means for rea pivotally sup orted latch retaining means 20 adapted to be moved by said element to release said latch, spring means biasing said retaining means against movement by said element, stop means for normally preventing said element from being subjected to the force of said spring biasing means except during the tripping operation, and means for relieving said element from the force exerted by said spring biasing means immediately following the release of said latch by said latch retaining means.

16. In a trip device for a circuit interrupter, an electro-responsive element, a latch, a latch retaining means engaging and holding said latch against movement and adapted to be moved by said element to release said latch, a spring con- 85 nected between said latch and said latch retaining means for biasing said retaining means to the latch-retaining position, and said spring being connected to said latch at a point movable in such direction as to render said spring ineffective im- 40 mediately following the release of said latch by said retaining means.

17. In a, trip device for a circuit interrupter, a thermally responsive element of bimetallic material, a tripping means adapted to be actuated thereby, a spring biasing said tripping means to the untripped position, said spring being connected at one end to an element of the device which moves when the device is tripped in such direction as to reduce the force exerted by said spring as soon as said tripping means has been moved to the tripped position by said thermally responsive element.

` HILLER D. DORFMAN. 

